Based on my recent personal experience, it's based on more than just the commonly measured parameters. Yes, get that all under control and stable, but I wouldn't recommend adding SPS until the system has been running long enough to reach a reasonable level of 1) Stability and 2) Bio-Diversity. If your rocks are shiny and new, you may have a hard time with SPS. Give it a couple months, and wait until your rocks color up a bit and you have some visible critters living in your sand and on your rocks.
Your mileage may vary.
My new tank just passed the 2.5 month mark, and the rock was cycling for nearly a month prior to that in a brute container. Only in the last few weeks have I started to see some SPS doing well in the tank.
If you just have to add something earlier, like I did, consider the cheapest, easiest stuff like birdsnest, stylophora, hydnophora and monitporas. Plenty of fun to be had with those, lots of colors and shapes to choose from.